In fluid transfer and routing systems, valves are extensively used to control delivery and otherwise regulate fluid flow. Frequently, proper valve operation and fast and reliable recognition of valve failures are critical to fluid system reliability.
It is known in the art to detect valve failures by measuring characteristic parameters of the fluid being transported. However, such methods largely tend to be very elaborate and require complex testing and analysis methodologies to ensure accurate detection. Furthermore, implementing such failure detection methods tend to undesirably increase development costs, operational costs, system downtime, and, where relevant, retrofit costs.
It is also known to detect a valve failure in accordance with sensing the position of a valve and comparing the sensed valve position to an expected valve position. Conventional valve position sensors, however, such as limit switches and potentiometers, often have low reliability because of their reliance on electrical contacts, which tend to wear and deteriorate relatively quickly. Comparatively reliable sensors, such as rotary variable transformers and linear variable differential transformers, are typically expensive. Other position sensors, such as eddy current sensors, Hall effect sensors, proximity sensors, and the like typically only operate in a limited temperature range.
To address these drawbacks of conventional position sensors, a cantilever-type position sensor, which in one embodiment is based on ceramic on metal technology described in U.S. Pat. No. 4,794,048, has been developed and described in U.S. Pat. No. 6,308,723. In such a position sensor, a deflectable sensing “beam” is cantilever-mounted to a main body, via a clamping force. In one configuration, the beam includes a thin metal substrate on which piezo-resistive components, the resistance of which change when strained, are disposed and coated with and fixed by means of glass or ceramic. The inventors of this application have found that such a configuration may exhibit wide variability in performance depending on clamping materials and method of assembly, resulting in expensive and labor-intensive assembly processes with poor yield and lack of part to part consistency. The inventors of this application have found that a cause of this problem is the non-uniformity of interfaces between the clamp and ceramic/glass coating on the beam.